GI 1: Upper GI tract Flashcards
Outline type of muscle found throughout the oesophagus?
cervical oesophagus = skeletal
upper and middle thoracic = skeletal/smooth
lower thoracic = smooth
Important structures in oesophagus that control how food when swallowed gets to the stomach?
upper and lower oesophageal sphincters
Where does the oesophagus start and end?
Starts C5 ends T10
What contributes to the lower oesophageal sphincter?
left and right crux of diaphragm, intact phreno-oesophageal ligament, angle of His and 3-4 cm of distal oesophagus is within abdomen - this all contributes anatomically to the LOS
What are the phases of swallowing?
oral phase, pharyngeal phase, upper oesophageal phase and lower oesophageal phase
Briefly outline the process of swallowing.
- chewing + saliva to prepare bolus, both oesophageal sphincters constricted
- bolus propelled to oesophagus, UOS opens reflexly, LOS opens by vasovagal reflex
- UOS closes, circular and longitudinal muscle contracts
- LOS closes as food passes through
How do the circular muscle work to allow food down the oesophagus during the upper oesophageal phase?
superior circular muscle rings contract and inferior rings dilate
What determines oesophageal motility?
pressure measurements
What is the approx. resting pressure of LOS?
~20mmHg
What happens to the pressure of the LOS during receptive relaxation?
decreases to <5 mmHg - mediated by inhibitory noncholinergic, noradrenergic (NCNA) neurons of myenteric plexus
Dysphagia =
difficulty in swallowing - localisation is important e.g. proximal or distal
Possible types of dysphagia?
- solids or fluids
- intermittent or progressive
- precise or vague in appreciation
Odynophagia =
pain on swallowing
Regurgitation =
return of oesophageal contents from above an obstruction (functional or mechanical)
Reflux =
passive return of gastroduodenal contents to mouth
What are the 2 main causes of functional disorders of oesophagus?
- abnormal oesophageal contraction
2. failure of protective mechanisms for reflux
What can abnormal oesophageal contraction cause?
hypermotility, hypomotility, disordered coordination
What can failure of protective mechanisms for reflux cause?
GORD
Hypermotility of the lower oesophageal sphincter is most commonly seen in?
Achalasia
What is achalasia?
When the LOS fails to open during swallowing leading to a backup of food within the oesophagus
How does achalasia lead to the LOS not opening?
loss of ganglion cells in Aurebach’s myenteric plexus in LOS wall leads to decreased activity of inhibitory NCNA neurones
What are the causes of achalasia?
primary aetiology unkown
secondary causes include diseases causing motor abnormalities similar to primary achalasia e.g. Chaga’s disease, protozoa infection, oesophagitis
How does achalasia progress eventually lead to the stop of peristalsis?
without inhibition the resting pressure of the LOS is higher than normal. This means the receptive relaxation phase sets in late and is too weak as the pressure in the LOS is higher than the stomach. Swallowed food stays in the oesophagus so pressure starts increasing throughout and the oesophagus starts to dilate. Eventually peristaltic waves stop propagating.
What type of onset does achalasia have?
insidious onset - symptoms can last for years without getting help
